Metal oxide coatings

ABSTRACT

Compounds of formula I may be hydrolyzed to produce metal oxides 
     
       
         
         
             
             
         
       
     
     wherein 
     M is Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Cd, In, Sn, Sb, La, Hf, Ta, W, Re, Os, Ir, Pt, Hg, Tl, Pb, Bi, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, U, or Pu; 
     X is O 1/2  or OR; 
     R is alkyl; 
     R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , and R 7  are independently H, alkoxy, C 1 -C 10  alkyl, phenyl or 
     
       
         
         
             
             
         
       
     
     R 10 , R 11 , R 12 , R 13 , R 14  and R 15  are independently C 1 -C 10  alkyl or phenyl; 
     n is equal to the the value of the oxidation state of M minus q; 
     m and p are independently 0 or an integer from 1 to 5; and 
     q is 0, 1, 2, or 4; 
     with the proviso that
         when q is 1, X is OR; and   when q is 2, X is O 1/2 , and M is V, Cr, Mn, Fe, As, Nb, Mo, Tc, Ru, Sb,   Ta, W, Re, Os, Ir, Pt, Bi, Th, U, or Pu; and   when q is 4, X is O 1/2 , and M is Cr, Mo, W, Ru, Re, Os, U, or Pu.
 
Articles comprising at least one metal oxide are fabricated by coating a substrate with at least one compounds of formula I before hydrolyzing, and/or heating the compound at a temperature ranging from about 50° C. to about 450° C.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional of and claims priority from U.S.Provisional Patent Application Ser. No. 60/945,715, filed on Jun. 22,2007, the entire contents of which is incorporated herein by reference.

BACKGROUND

Transparent conductive oxides (TCO) are electronic materials that findutilization in a large variety of optoelectronic devices including, butnot limited to flat panel displays, liquid crystal displays, plasmadisplays, electroluminescent displays, touch panels and solar cells.These materials also used as antistatic coatings and electromagneticinterference (EMI) shielding. TCOs are of crucial importance for anumber of emerging technologies, such as organic electroluminescentdevices (both displays and lighting devices), photovoltaic (PV) devices,including crystalline-Si heterojunction with intrinsic thin layer,amorphous silicon, CdTe, Culn(Ga)Se₂ (CIGS), and organic photovoltaics.TCOs act as transparent conducting windows, structural templates, anddiffusion barriers TCOs are also used for various optical coatings, inparticular as infra-red reflecting coatings (heat mirrors) in automotiveand building industries. Although the main desirable characteristics ofTCO materials are common to many technologies, including high opticaltransmissivity across a wide range of light spectrum and low electricalresistivity, specific TCO parameters vary from one system to another.Emerging technologies require new types of transparent conductors withproperties better adjusted to their needs. The number of compositionscurrently used as TCOs is restricted to a few primary and binarysystems. This is mainly because of two factors: 1) limited bulksolubility of crystalline metal oxide phases in each other, and 2)certain technical limitations of the currently used methods. If thesechallenges could be overcome, it has been shown that the number ofsuitable transparent and conductive binary, ternary and even quaternaryphases may be larger (A. J. Freeman, K. R. Poeppelmeier, T. O. Mason, R.P. H. Chang, and T. J. Marks, MRS Bulletin, 45-51, August 2000). Some ofthem may potentially exist in thin films only since the phase separationin this case is kinetically precluded by the film thinness.

A convenient way to make a large variety of multicomponent TCOs islow-pressure or high-pressure CVD using solid volatile organometallicprecursors. However, CVD requires high substrate temperature (400-450°C.) needed for precursor decomposition. Despite the fact that thismethod can be applied for large area production, it is limited tothermally stable substrates (like glass and metal foils) and cannot beapplied for direct TCO layer deposition onto such light absorbers asCIGS, CdTe, and organic PVs.

TCO's are commercially fabricated by magnetron sputtering. Otherphysical deposition techniques (electron beam evaporation, pulsed laserdeposition, etc.) can also be applied. It is widely recognized thatsputtering provides the best results in terms of high opticaltransparency and electrical conductivity of metal-oxide films,particularly ITO, ZnO, and ZnO—Al₂O₃. However, expensive vacuumequipment, high energy consumption (˜30 kW/m²), and batch production allcontribute into the high technology cost. Additionally, PVD technologiesimpose certain limitations on the development of multicomponent (morethan two) TCOs because of technical difficulties in controlling uniformelement distribution, and thus the consistency of material properties,over time. As a result, PVD methods are not well suited for developmentof new TCO formulations for emerging PV systems. The progress in thisarea is a subject of method versatility and flexibility.

Accordingly, there is a need for solution-based technologies, which havethe additional benefit of process cost reduction, as compared to PVD,being well suited for fast continuous roll-to-roll fabrication.

Solution-based preparation of different parts of PV devices (amorphoussilicon layer, CIGS layer, organic PVs, CdS junction layer, TCO) hasrecently been the subject of intensive research. While noticeableprogress has been achieved by both academia and industry inhigh-throughput fabrication of various PV components, suitablesolution-based low-temperature TCO production remains a challenge andcould be the ultimate barrier to fully solution-processed PVs. Aconsiderable amount of effort has been devoted to developing printedTCOs. Despite certain progress in this field, none of the commercializedmaterials are used for PV devices mostly because of inferiorconductivity-transparency properties when compared to those TCO'sproduced by sputtering. Known wet methods have limitations, whichpreclude them from reaching the goals imposed by PV technologies: sheetresistance of <7 Ω/, optical transmissivity >90% in near UV-visible-nearIR regions of light spectrum, and low haze.

A number of approaches have been tried to fabricate TCOs by wetprocesses. Sol-gel processes are relatively slow, proceeding via aporous sediment formation and requiring high temperature for the filmcrystallization and densification. The chemical nature of this processdoes not allow for fabrication of high quality TCO. Metal-organicsdecomposition can be done relatively fast, but like CVD, requires hightemperature for precursor degradation. This method starts from thedeposition of a dilute solution or a slurry of precursor(s) in a liquidcarrier, and results in the formation of porous films. Nano-solutioninks for ITO fabrication have been widely commercialized for low-endapplications. Their use for PV devices is still far from reality, firstbecause of high temperature needed for sintering nano-particles, andsecond, because of insufficient conductivity-transparency performance.The latter is an inherent problem of sintering process, since theboundaries between the original particles cannot be completelyeliminated at temperatures below 450° C. These boundaries are the reasonfor low carrier concentration, low charge mobility, and high haze.Oxidative spray pyrolysis is widely used for FTO (fluorinated tin oxide)and ATO (antimony-tin oxide) fabrication. It can be also used for ZnO,and possibly for other TCOs. Besides high temperature (450-550° C.)requirements, this method is not capable of high-end TCO filmfabrication.

Thus, a versatile, flexible, low temperature, low cost wet process forfabrication of a wide variety of TCOs is desirable. Such a process wouldnot only allow reduced TCO cost and fabrication of flexible devices, butalso TCOs with properties that may be better adjusted for particulartechnology needs, resulting in improved device efficiency.

SUMMARY

In one aspect, the present invention relates to compounds of formula I

wherein

M is Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Y,Zr, Nb, Mo, Tc, Ru, Rh, Pd, Cd, In, Sn, Sb, La, Hf, Ta, W, Re, Os, Ir,Pt, Hg, Tl, Pb, Bi, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu,Th, U, or Pu;

X is O_(1/2) or OR;

R is alkyl;

R¹, R², R³, R⁴, R⁵, R⁶, and R⁷ are independently H, alkoxy, C₁-C₁₀alkyl, phenyl or

R¹⁰, R¹¹, R¹², R¹³, R¹⁴ and R¹⁵ are independently H, C₁-C₁₀ alkyl orphenyl;

n is equal to the value of the oxidation state of M minus q;

m and p are independently 0 or an integer from 1 to 5; and

q is 0, 1 2, or 4;

with the proviso that

-   -   when q is 1, X is OR;    -   when q is 2, X is O_(1/2), and M is Ti, V, Mn, Nb, Mo, Tc, Ru,        Sb, Ta, W, Re, Os, Th, or U; and    -   when q is 4, X is O_(1/2), and M is Cr, Mo, W, Ru, Re, Os, U, or        Pu.

The metallic center of the compounds of formula I may be optionallycoordinated with a Lewis base such as acyclic or cyclic ethers, amines,phosphines, arsines, or sulfides. For example, Zn compounds, some ofwhich are solid in non-coordinated forms, may be liquids when complexedwith ether, THF, or triethylamine.

In another aspect, the present invention relates to processes forfabricating an article comprising at least one metal oxide byhydrolyzing at least one compound of formula I. The process mayadditionally include coating a substrate with the compound beforehydrolyzing, and/or heating the compound at a temperature ranging fromabout 50° C. to about 450.

Advantages of the process of the present invention include: relativelyinexpensive starting materials, relatively low process temperatures, lowprocess cost, high quality film formation, ability to fabricatemulticomponent films, applicability to a variety of substrates becauseof good wetting properties of the compounds of formula I, printability,exact control of component stoichiometry, and easy tunability of processparameters and material properties.

Metal trialkylsilyloxy derivatives of formula M(OSiMe₃)_(x), where M isTi, Zr, Nb, Tl, Hf, Sn, and Al, and x is the value of the valence of M,are known (Journal of the Chemical Society, (1959), 3404-11; Chemistry &Industry (1958), 17) Tetrakis(trimethylsiloxy)titanium has beenhydrolyzed in dioxane to yield poly(trimethylsiloxano-titanoxanes)(Canadian J. Chemistry (1963), 41 629-35). These materials typically donot produce uniform films when applied directly to a substrate or fromsolution.

DETAILED DESCRIPTION

The present invention relates to compounds of formula I, and their usein preparing metal oxides. Embodiments of the compounds of formula Iinclude metal siloxanolates (where q is 0) of formula

metal alkoxide siloxanolates (where q is 1) of formula

metal oxide siloxanes (where q is 2) of formula

and metal oxide siloxanes (where q is 4) of formula

In particular embodiments the compounds of the present invention are offormula

wherein R^(1a), R^(3a), R^(4a), R^(5a), and R^(7a) are H or C₁-C₁₀alkyl, preferably methyl.

For many embodiments of the present invention, preferred substituents(R¹⁻⁷and R^(1a-7a)) for the compounds are C₁-C₁₀ alkyl; more preferredis methyl. Preferred metals are Mg, Al, Sc, Ti, V, Zn, Ga, Y, Zr, Mo,Cd, In, Sn, Sb, Ce, Gd, Lu, and W. More preferred metals are Al, Ga, Sc,Y, Ti, V, Zn, Cd, In, Sb and Sn.

Specific embodiments of the compounds of formula I includeTi(OSi(CH₃)₂OSi(CH₃)₃)₄, Al(OSi(CH₃)₂OSi(CH₃)₃)₃,Ga(OSi(CH₃)₂OSi(CH₃)₃)₃, VO(OSi(CH₃)₂OSi(CH₃)₃)₃,Zn(OSi(CH₃)₂OSi(CH₃)₃)₂, Sn(OSi(CH₃)₂OSi(CH₃)₃)₄, andIn(OSi(CH₃)₂OSi(CH₃)₃)₃.

Methods for preparing the compounds of formula I include the followingreactions:

X_(q)M(OR)_(n)+n ZOAc=>X_(q)M(OZ)_(n)+n ROAc   (1)

wherein Z is

M, R, R¹—R⁷, m, q and n are as defined above.

Metals for which compounds of formula I may be prepared via reaction 1include, for example, Zn, Al, In, Ti, Zr, V, Ga, Sc, Y, La, thelanthanides, Bi(III), and especially Zn, Al, In, Ti, Zr, and V.Exemplary R groups include ispropyl and n-butyl.

MX¹ _(n)+n ZOH+n NR₃→M(OZ)_(n)+nNR3H+X—  (2)

wherein M and Z are as defined above, X¹ is halo, and NR₃ is anyalicyclic, cyclic or polycyclic amine which easily forms a hydrochloridesalt, such as trialkylamines, pyridine, hexamethylenediamine.

Metals for which compounds of formula I may be prepared via reaction 2include, for example, Sn(IV), Pb(IV), Sb(V), Nb(V), and Ta(V),especially Sn.

MR_(n)+nZOH→M(OZ)_(n)+nRH   (3)

wherein M, R, n, and Z are as defined above.

Metals for which compounds of formula I may be prepared via reaction 3include, for example, Mg, Zn, In, Al, Ga and Hg. Examples of compoundsof formula MR_(n) that may be used in reaction 3 include MgBu₂, ZnEt₂,InBu₃, AlBu₃, GaBu₃, HgMe₂. Exemplary R groups include ethyl and butyl.

The compounds of the present invention are typically liquids withexcellent wetting properties on substrates of interest and/or soluble incommon organic solvents and may be conveniently applied by commoncoating methods. In addition, they are typically stable in dry air atroom temperature, so they may be handled without any specialprecautions. When exposed to humid air at elevated temperatures,typically 50° C.-450° C., preferably 100° C.-200° C., the compounds areconverted into metal oxides by hydrolysis with atmospheric moistureand/or thermal disproportionation. Byproducts are volatile low molecularweight siloxanes, which may be easily sequestrated.

Accordingly, in another aspect, the present invention relates to aprocess for fabricating an article that includes a metal oxide, byhydrolyzing a compound of formula I. The metal oxides includemonometallic and polymetallic oxides and doped oxide matrix systems,including, for example, ZnO, CdO, In₂O₃, SnO₂, Al₂O₃, Ga₂O₃, and Sb₂O₅,binary, ternary, and quaternary oxides based thereon, and thematrix-dopant systems listed in Table 1.

TABLE 1 Matrix Dopant or Compound ZnO Al, Y, Sc, Ti, Zr ZnO—SnO₂Zn₂SnO₄, ZnSnO₃ SnO₂ BaSnO₃, SrSnO₃, Sb TiO₂ BaSnO₃, SrSnO₃, V In₂O₃ Zn,Sn, Ga, AlPreferred metal oxides are TCOs. Oxides that include more than onemetallic element may be prepared by combining one or more compounds offormula I and hydrolyzing the mixture.

In the process of the present invention, the compounds of formula I arehydrolyzed by heating at a temperature ranging from about 50° C. toabout 450° C. in the presence of water vapor. Relative humiditytypically ranges from about 5% to about 100%, preferably from about 5%to about 75%, and more preferably from about 10% to about 55%. Verylittle water is typically required, as other reactions that producemetal oxides and/or water may occur during the process. For example,dimerization of siloxanols released by the hydrolysis reaction may yieldwater, which can hydrolyze additional metal-ligand bonds (equations 4and 5).

M(OSiMe₂OSiMe₃)_(n)+2 H₂O→MO_(n)+n Me₃SiOSiMe₂OH   (4)

4 Me₃SiOSiMe₂OH→2 Me₃SiOSiMe₂OSiMe₂OSiMe₃+2 H₂O   (5)

Metal-siloxane derivatives may undergo thermal rearrangement by reaction(6) without added water.

M(OSiMe₂OSiMe₃)_(n)→MO_(n)+Me₃SiOSiMe₂OSiMe₂OSiMe₃   (6)

Thermal rearrangement with the formation of metal-methyl bond andunstable siloxanone (reaction 7) may also yield metal-alkyl fragmentsthat may be hydrolyzed even faster than metal siloxanolates.

M(OSiMe₂OSiMe₃)_(n)→MMe(OSiMe₂OSiMe₃)_(n−1)+Me₃SiOSi(Me)═O   (7)

Acid catalysts may also increase the rate of the hydrolysis. Suitableacids include organic acids such as acetic acid, propionic acid andbutyric acid. The amount of acid typically ranges from about 0.01 ppm toabout 1000 ppm, based on total weight, preferably from about 0.1 ppm toabout 10 ppm.

The process of the present invention may additionally include coating asubstrate with the compounds of formula I before hydrolyzing. Substratesfor use in the process are only limited by their suitability for the enduse, and may include glass, ceramics, plastics, metals, alloys, wood,paper, graphite, textiles, organic or inorganic substrates, such asvarious components of optical, electronic, or opto-electronic devices.Any method for producing a thin film on a substrate may be used,including conventional coating methods such as, but not limited to spincoating, dip coating, spray coating, and printing techniques, such asscreen printing, ink-jet printing, gravure and rotogravure printing,flexography, offset printing, laser printing and pad printing. Thecoating or printing method and its parameters may affect properties ofthe film, such as thickness and uniformity, and may be adjusted toachieve a desired result. Parameters that may be adjusted may include,for example, type of solvent, precursor concentration, material amount,spin rate and spin time (for spin-coating), residence time (dipping andspray), and other relevant parameters, as will be apparent to theskilled in the art.

The compounds of formula I may be applied as neat liquids whereapplicable, in solvents or solvent mixtures that are relatively volatileat process temperatures. The solvent may affect both hydrolysis kineticsand film properties. Polar and water miscible solvents may promotefaster hydrolysis. Suitable solvents include alkanes such as hexanes,heptane, and octane; aromatics such as benzene, toluene, xylenes;dialkyl ethers such as dipropyl ether, diisopropyl ether, di-t-butylether, and dibutyl ether, monoglyme, and diglyme; cyclic ethers such as1,4-dioxane, 1,3-dioxane, furan, tetrahydrofuran, pyran,tetrahydropyran, and the like; ketones such as acetone,methylethylketone, cyclohexanone; dimethylformamide, demethylacetamide,and mixtures thereof. Preferred solvents are hexanes, toluene anddimethylformamide. A suitable amount of water, preferably purifiedwater, may be added to the solution if desired in any manner, prior to,during, or subsequent to the preparation of the solution.

Where the substrate is heat-resistant, an additional annealing step maybe performed. Annealing temperature ranges from about 200° C. to about450° C.

Due to their good wetting properties, the compounds of formula Itypically form uniform continuous liquid films on substrates. Afterhydrolysis/thermolysis and, if desired, annealing, they are convertedinto thin uniform metal oxide films. Adhesion of the films to thesubstrate may depend on the substrate nature and film thickness, but istypically good for films thinner than 0.5 microns.

The process of the present invention provides articles that includemetal oxide coatings, particularly articles that include conductive orsemiconductive metal oxide coatings, particularly thin film coatingswhich, depending on the nature of metal oxide, have high refractiveindex, high catalytic/photocatalytic activity, electrically conductiveor semiconductive properties, non-linear optical properties, switchingproperties, barrier properties, and/or binding properties. The processmay be used for production of transparent semiconductors and electrodes,sensors, high refractive index surfaces, such as windows, optics,ceramics, elements with non-linear optical properties, anti-reflectivecoatings, self-cleaning windows, elements with catalytic properties forNOx reduction and/or removing sulfur from oil and fuels, protectivecoatings, anti-corrosion coatings, anti-static coatings, and barriercoatings for excluding organics, moisture, and/or gases. The process mayalso be used for fabricating transparent electrodes for photovoltaicdevices, flat panel displays, touch panels, OLEDs, gradient refractiveindex layers in LED lamps and OLEDs, hole plugging in solid state fuelcell blocks, binding preformed metal oxide powders, such as titaniareflective coatings, and dye sensitized solar cells. Final properties ofthe coatings depend on the nature of the metal oxide.

In the context of the present invention, alkyl is intended to includelinear, branched, or cyclic hydrocarbon structures and combinationsthereof, including lower alkyl and higher alkyl. Preferred alkyl groupsare those of C₂₀ or below. Lower alkyl refers to alkyl groups of from 1to 6 carbon atoms, preferably from 1 to 4 carbon atoms, and includesmethyl, ethyl, n-propyl, isopropyl, and n-, s- and t-butyl. Higher alkylrefers to alkyl groups having seven or more carbon atoms, preferably7-20 carbon atoms, and includes n-, s- and t-heptyl, octyl, and dodecyl.Cycloalkyl is a subset of alkyl and includes cyclic hydrocarbon groupsof from 3 to 8 carbon atoms. Examples of cycloalkyl groups includecyclopropyl, cyclobutyl, cyclopentyl, and norbornyl. Alkenyl and alkynylrefer to alkyl groups wherein two or more hydrogen atoms are replaced bya double or triple carbon-carbon bond, respectively.

Aryl and heteroaryl mean a 5- or 6-membered aromatic or heteroaromaticring containing 0-3 heteroatoms selected from nitrogen, oxygen orsulfur; a bicyclic 9- or 10-membered aromatic or heteroaromatic ringsystem containing 0-3 heteroatoms selected from nitrogen, oxygen orsulfur; or a tricyclic 13- or 14-membered aromatic or heteroaromaticring system containing 0-3 heteroatoms selected from nitrogen, oxygen orsulfur. The aromatic 6- to 14-membered carbocyclic rings include, forexample, benzene, naphthalene, indane, tetralin, and fluorene; and the5- to 10-membered aromatic heterocyclic rings include, e.g., imidazole,pyridine, indole, thiophene, benzopyranone, thiazole, furan,benzimidazole, quinoline, isoquinoline, quinoxaline, pyrimidine,pyrazine, tetrazole and pyrazole.

Arylalkyl means an alkyl residue attached to an aryl ring. Examples arebenzyl and phenethyl. Heteroarylalkyl means an alkyl residue attached toa heteroaryl ring. Examples include pyridinylmethyl andpyrimidinylethyl. Alkylaryl means an aryl residue having one or morealkyl groups attached thereto. Examples are tolyl and mesityl.

Alkoxy or alkoxyl refers to groups of from 1 to 8 carbon atoms of astraight, branched, cyclic configuration and combinations thereofattached to the parent structure through an oxygen. Examples includemethoxy, ethoxy, propoxy, isopropoxy, cyclopropyloxy, and cyclohexyloxy.Lower alkoxy refers to groups containing one to four carbons.

Acyl refers to groups of from 1 to 8 carbon atoms of a straight,branched, cyclic configuration, saturated, unsaturated and aromatic andcombinations thereof, attached to the parent structure through acarbonyl functionality. One or more carbons in the acyl residue may bereplaced by nitrogen, oxygen or sulfur as long as the point ofattachment to the parent remains at the carbonyl. Examples includeacetyl, benzoyl, propionyl, isobutyryl, t-butoxycarbonyl, andbenzyloxycarbonyl. Lower-acyl refers to groups containing one to fourcarbons.

Heterocycle means a cycloalkyl or aryl residue in which one to two ofthe carbons is replaced by a heteroatom such as oxygen, nitrogen orsulfur. Examples of heterocycles that fall within the scope of theinvention include pyrrolidine, pyrazole, pyrrole, indole, quinoline,isoquinoline, tetrahydroisoquinoline, benzofuran, benzodioxan,benzodioxole (commonly referred to as methylenedioxyphenyl, whenoccurring as a substituent), tetrazole, morpholine, thiazole, pyridine,pyridazine, pyrimidine, thiophene, furan, oxazole, oxazoline, isoxazole,dioxane, and tetrahydrofuran.

Substituted refers to residues, including, but not limited to, alkyl,alkylaryl, aryl, arylalkyl, and heteroaryl, wherein up to three H atomsof the residue are replaced with lower alkyl, substituted alkyl, aryl,substituted aryl, haloalkyl, alkoxy, carbonyl, carboxy, carboxalkoxy,carboxamido, acyloxy, amidino, nitro, halo, hydroxy, OCH(COOH)₂, cyano,primary amino, secondary amino, acylamino, alkylthio, sulfoxide,sulfone, phenyl, benzyl, phenoxy, benzyloxy, heteroaryl, orheteroaryloxy.

Haloalkyl refers to an alkyl residue, wherein one or more H atoms arereplaced by halogen atoms; the term haloalkyl includes perhaloalkyl.Examples of haloalkyl groups that fall within the scope of the inventioninclude CH₂F, CHF₂, and CF₃.

Siloxy refers to saturated linear, branched or cyclic structures andcombinations thereof, based on a backbone having alternating silicon andoxygen atoms, each silicon atom separated from its nearest siliconneighbors by single oxygen atoms and substituted with 0-3 hydrogen,halo, alkyl or aryl groups.

EXAMPLES Example 1 Synthesis of Ti(OSi(CH₃)₂OSi(CH₃)₃)₄

Freshly distilled titanium isopropoxide (9 g, 31.66 mmol, Aldrich) wasmixed with 250 ml of dry cyclohexane in a 500-ml three-neck round bottomflask equipped with a thermometer, addition funnel, magnetic stirringand a Liebig condenser attached to argon-vacuum line. The mixture washeated to 55-60° C., and 26.5 g of acetoxypentamethyldisiloxane (0.128mol, used as purchased from Gelest Co., Morrisville Pa.) in 50 ml of drycyclohexane were added dropwise during 1 hour under vigorous stirring.The mixture was heated to 55-60° C. for additional 2 hours and wasallowed to cool down to room temperature. Volatiles were removed underreduced pressure. The residue was distilled at 80-82° C./0.05 torr toafford 13.5 g of colorless light liquid Ti(OSi(CH₃)₂OSi(CH₃)₃)₄.Refractive index (n_(D) ²⁰) of Ti(OSi(CH₃)₂OSi(CH₃)₃)₄ measured withAbbe refractometer at 25° C. was 1.413.

Example 2 Synthesis of Al(OSi(CH₃)₂OSi(CH₃)₃)₃

Aluminum isopropoxide (8.6 g, 42.11 mmol, from Gelest Co.) was dissolvedin 250 ml of dry cyclohexane in a 500-ml three neck round bottom flaskequipped with a thermometer, addition funnel, magnetic stirring and aLiebig condenser attached to argon-vacuum line. The mixture was heatedto 55-60° C., and 26.5 g of acetoxypentamethyldisiloxane (0.128 mol) in50 ml of dry cyclohexane were added dropwise during 1 hour undervigorous stirring. The mixture was heated to 55-60° C. for additional 2hours and was allowed to cool down to room temperature. Volatiles wereremoved under reduced pressure. An oily residue was added dropwise toshort-path distillation apparatus at 170-180° C./0.02 torr. 8.7 g ofcolorless oily Al(OSi(CH₃)₂OSi(CH₃)₃)₃ was obtained after distillation.

Example 3 Synthesis of VO(OSi(CH₃)₂OSi(CH₃)₃)₃

Vanadium triisopropoxide oxide (10.3 g, 42.18 mmol, Gelest Co.) wasmixed with 250 ml of dry cyclohexane in a 500-ml three neck round bottomflask equipped with a thermometer, addition funnel, magnetic stirringand a Liebig condenser attached to argon-vacuum line. The mixture washeated to 55-60° C., and 26.5 g of acetoxypentamethyldisiloxane (0.128mol) in 50 ml of dry cyclohexane were added dropwise during 1 hour undervigorous stirring. The mixture was heated to 55-60° C. for additional 2hours and was allowed to cool down to room temperature. Volatiles wereremoved under reduced pressure. The residue was distilled at 40-42°C./0.015 torr to afford 12.2 g of yellowish light liquidVO(OSi(CH₃)₂OSi(CH₃)₃)₃.

Example 4 Synthesis of Zn(OSi(CH₃)₂OSi(CH₃)₃)₂

A 0.1 M solution of diethylzinc in heptane (40 ml, Aldrich) wastransferred into a 500-ml three-neck round bottom flask equipped with athermometer, addition funnel, magnetic stirring and a Liebig condenserattached to argon-vacuum line. Anhydrous isopraponol (6 ml, Aldrich) wasslowly added under vigorous stirring. Additional 50 ml of anhydrousisopropanol were added and the mixture was refluxed for 1 hour.Volatiles were removed under reduced pressure affording whitecrystalline zinc isopropoxide, which was dried under vacuum at 80° C.for an hour. Dry cyclohexane (250 ml ) was added into the flask, and thesolid quickly dissolved. The mixture was heated to 55-60° C., and 17.0 gof acetoxypentamethyldisiloxane (82 mmol) in 50 ml of dry cyclohexanewas added dropwise during 1 hour under vigorous stirring. The mixturewas heated to 55-60° C. for additional 2 hours and was allowed to coolto room temperature. Volatiles were removed under reduced pressure. Asolid waxy residue was dried under vacuum at 50° C., then wastransferred into a sublimation apparatus, and was sublimed at 110°C./0.02 torr to afford 9.7 g of white solid Zn(OSi(CH₃)₂OSi(CH₃)₃)₂.

Example 5 Synthesis of Me₃SOSiMe₂OH

Pentamethyldisiloxane (25 g, 0.168 mol, Gelest Co.) was slowly added to50 ml of monoglyme containing 3.5 g of water and 1 g of 10% Pd/C undervigorous stirring. After gas release had ceased, the mixture was driedwith anhydrous MgSO₄ and filtered through a sintered glass filter. Thefiltrate was stirred with CaH₂ for 1 hour, and was distilled at 50° C.under reduced pressure. The content of pentamethyldisiloxanol indistillate was determined by 1H NMR analysis.

Example 6 Synthesis of Sn(OSi(CH₃)₂OSi(CH₃)₃)₄

A 1.0 M solution of SnCl₄ in heptane (20 ml, Aldrich) were dissolved in300 ml of dry hexanes. Dry triethylamine (15 ml, 0.108 mol) was added,and the mixture was stirred for 10 min. 11.87 g ofpentamethyldisiloxanol (0.08 mol, solution in monoglyme) were added in afew portions, and the mixture was stirred for 1 hour at roomtemperature. The mixture was filtered through a sintered glass filter,and the filtrate was refluxed for 1 hour. The mixture was cooled to roomtemperature and filtered again. Volatiles were removed under reducedpressure, and finally under vacuum. The residue was centrifuged toseparate a dark-yellow heavy oil from supernatant colorlessSn(OSi(CH₃)₂OSi(CH₃)₃)₄, yield about 75%

Example 7 Synthesis of In(OSi(CH₃)₂OSi(CH₃)₃)₃

InCl₃ (10 g, 45.2 mmol, Aldrich) was dissolved in 150 ml of dry toluene.In order to remove traces of water coming with InCl₃, the solution wassubjected to slow distillation under nitrogen until the point when thedistillation temperature reached 108° C. The solution was cooled to 0°C. 68 ml of 1.0 M Mg(Bu)₂ solution in heptane (Aldrich) was slowly addedto InCl₃ at 0° C. under vigorous stirring. After the addition wascompleted, the mixture was stirred for 2 hrs at 70° C. Solids wereseparated by filtration. The filtrate was distilled first at ambientpressure to remove the most part of solvents, and then at 0.1 torr. Afraction boiling at 70-72° C./0.1 mm Hg was collected. 12.1 g of InBu₃were obtained. This material was dissolved in 200 ml of dry hexane, and19 g of pentamethyldisiloxanol (0.128 mol, solution in monoglyme) wereslowly added to the reaction mixture. After the addition was completed,the mixture was stirred for 1 hour and then refluxed for additional 2hours providing safe escape way for butane release. Volatiles wereremoved under reduced pressure. The residue was distilled as describedfor Al(OSi(CH₃)₂OSi(CH₃)₃)₃, yield >90%.

Examples 8-11 Preparation of Transparent Oxide-Coated Substrate

A 4-inch silicon wafer was spin-coated with 5 wt % solution ofTi(OSi(CH₃)₂OSi(CH₃)₃)₄ in hexane at 2 krpm/30 sec. The wafer was placedinto a 150° C. oven for 1 hour. Refractive index (n_(D) ²²) of theresulted coating measured with an ellipsometer was 1.721 at 30nanometers thickness. After an additional 6 hrs treatment at 150° C.,the refractive index of the resultant coating 1.782 at 30 nanometersthickness. After additional treatment for 6 hours at 450° C., therefractive index of the resultant coating was 2.122 at 27 nanometersthickness.

A 10 wt % solution of Al(OSi(CH₃)₂OSi(CH₃)₃)₃ in dry hexanes was spincoated on glass slide @ 2 krpm/30 sec. The substrate was heated for 30min at 150° C. in air. A 150 nm thick transparent amorphous aluminumoxide layer was formed.

A 50 wt % solution of Al(OSi(CH₃)₂OSi(CH₃)₃)₃ in dry hexanes was spincoated on graphite slide @ 2 krpm/30 sec. The substrate was heated for30 min at 150° C. in air. A 300 nm thick transparent amorphous aluminumoxide layer was formed.

A 50 wt % solution of Sn(OSi(CH₃)₂OSi(CH₃)₃)₄ in dry hexanes was spincoated on glass slide @ 2 krpm/30 sec. The substrate was heated 1 hourat 150° C. in air. A 500 nm thick transparent amorphous tin oxide layerwas formed.

Example 12 Schottky Diode—ITO/TiOx/Au

A layer of Ti(OSi(CH₃)₂OSi(CH₃)₃)₄ was deposited onto ITO-coated,solvent and UV-ozone cleaned glass substrates via spin-coating liquidTi(OSi(CH₃)₂OSi(CH₃)₃)₄ at 4 krpm/100 sec, and baked for 1 hour at 200°C. in air. A gold electrode (500 A) was evaporated onto the resultingTiOx layer using a shadow mask. The device was immersed in boiling waterat pH 3 for about 10 minutes, and further dried in lab air.Current-voltage characteristics under both reversed and forward polaritybias were measured and rectification ratio of about 250 at bias voltageof 5V was observed. The rectification ratio of the device was found tobe 10× higher than reported in the literature for nano-TiOx multiplecoatings using conventional sol-gel process.[R. Konenkamp, Phys. Rev. B,vol. 61, 11057, 2000]

Example 13 Conductivity of ITO/polyoxide/Al

A 50 wt % hexane solution of a mixture of Ti(OSi(CH₃)₂OSi(CH₃)₃)₄ andVO(OSi(CH₃)₂OSi(CH₃)₃)₃ with Ti:V ratio 19:1 was prepared. The solutionwas spun onto ITO-coated, solvent and UV-ozone cleaned glass substratesat 2 krpm for 30 sec and baked for 15 min at 150° C. under inertatmosphere, to form a Ti(V)O_(x) layer of 250 nm thickness. The coatedsubstrate was immersed in boiling water at pH 3 for 10 minutes, was thenrinsed with deionized water, and was dried at 100° C. in air. Analuminum electrode (1000 A) was deposited via thermal evaporation ontoformed (Ti:V)O_(x) layer using a shadow mask. Current-voltagecharacteristics for a pure TiO₂ layer, a Ti(V)O_(x) layer beforehydrolysis, and the same after hydrolysis indicated a significantincrease in out-of-plane conductivity for Ti(V)O_(x), as compared withTiO_(x) coatings without the vanadium component.

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

1. A compound of formula I

wherein M is Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge,As, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Cd, In, Sn, Sb, La, Hf, Ta, W, Re,Os, Ir, Pt, Hg, Tl, Pb, Bi, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm,Yb, Lu, Th, U, or Pu; X is O_(1/2) or OR; R is alkyl; R¹, R², R³, R⁴,R⁵, R⁶, and R⁷ are independently H, alkoxy, C₁-C₁₀ alkyl, phenyl or

R¹⁰, R¹¹, R¹², R¹³, R¹⁴ and R¹⁵ are independently H, C₁-C₁₀ alkyl orphenyl; n is equal to the the value of the oxidation state of M minus q;m and p are independently 0 or an integer from 1 to 5; and q is 0, 1, 2,or 4; with the proviso that when q is 1, X is OR; and when q is 2, X isO_(1/2), and M is Ti, V, Mn, Nb, Mo, Tc, Ru, Sb, Ta, W, Re, Os, Th, orU; and when q is 4, X is O_(1/2), and M is Cr, Mo, W, Ru, Re, Os, U, orPu.
 2. A compound according to claim 1, of formula


3. A compound according to claim 1, of formula


4. A compound according to claim 1, of formula


5. A compound according to claim 1, of formula


6. A compound according to claim 1, of formula


7. A compound according to claim 1, wherein a Lewis base is coordinatedto M.
 8. A compound according to claim 1, wherein m and p are
 0. 9. Acompound according to claim 1, wherein M is Mg, Al, Sc, Ti, V, Zn, Ga,Y, Zr, Mo, Cd, In, Sn, Sb, Ce, Gd, Lu, or W.
 10. A compound according toclaim 1, wherein M is Al, Ga, Sc, Y, Ti, V, Zn, Cd, In, Sb or Sn.
 11. Acompound according to claim 1, wherein R¹, R², R³, R⁴, R⁵, R⁶, and R⁷are independently H or methyl.
 12. A compound according to claim 1,wherein R¹, R², R³, R⁴, R⁵, R⁶, and R⁷ are methyl.
 13. A compoundaccording to claim 1, of formula

wherein R^(1a), R^(3a), R^(4a), R^(5a), and R^(7a) are H or methyl. 14.A compound according to claim 1, of formula

wherein R^(1a), R^(3a), R^(4a), R^(5a), and R^(7a) are H or methyl. 15.A compound according to claim 1, of formula

wherein R^(1a), R^(3a), R^(4a), R^(5a), and R^(7a) are H or methyl. 16.A compound according to claim 1, of formula

wherein R^(1a), R^(3a), R^(4a), R^(5a), and R^(7a) are H or methyl. 17.A compound according to claim 1, of formula Ti(OSi(CH₃)₂OSi(CH₃)₃)₄. 18.A compound according to claim 1, of formula Al(OSi(CH₃)₂OSi(CH₃)₃)₃. 19.A compound according to claim 1, of formula VO(OSi(CH₃)₂OSi(CH₃)₃)₃. 20.A compound according to claim 1, of formula Zn(OSi(CH₃)₂OSi(CH₃)₃)₂. 21.A compound according to claim 1, of formula Sn(OSi(CH₃)₂OSi(CH₃)₃)₄. 22.A compound according to claim 1, of formula In(OSi(CH₃)₂OSi(CH₃)₃)₃. 23.An article fabricated using at least one compound of formula I.
 24. Anelectronic device fabricated using at least one compound of formula I.25. An electronic device according to claim 24 that is an optoelectronicdevice.